This application claims the priority of German Patent Application, Serial No. 199 19 271.5, filed Apr. 28, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a shift device of a change-speed gearbox of motor vehicles, and more particularly to a shift rocker used in a shift device.
In general, change-speed gearboxes are provided with synchronizing units known also as gear wheel clutches. During gearshift, a U-shaped shift rocker is used to axially displace a shift sleeve that interacts with the gear wheel clutch for optionally shifting a gear wheel when changing gears of the change-speed gearbox.
U.S. Pat. No. 5,802,916, issued on Sep. 8, 1998, describes a U-shaped shift rocker which is composed of at least two structural parts and encloses the shift sleeve by an angle of more than 180xc2x0. The shift rocker has parallel sidewalls which have end portions formed with receiving bores for guiding the shift sleeve via journals. At a radial distance to the receiving bores, the shift rocker is rotatably supported in pivot bearings which are formed by bolts fixedly arranged in the gearbox housing or in the shift device. The sidewalls are interconnected by a cross member which has attached thereon in the mid-section area of the shift rocker a driver which is guided along a longer region axially to the outer contour of the shift rocker. The driver has an angled portion which is formed with a recess to form a shift slot for a positive engagement of a shift finger which is fixedly secured to a shift shaft. The arrangement of the driver in the conventional shift rocker results in a force introduction offset to the center of the shift rocker, to realize a shifting, i.e. a rotation of the shift rocker. The shift rocker further includes, axially offset to the driver, a radial bracket for swingably mounting a locking lever of a locking unit. This conventional shift rocker is made up of many structural parts which are connected to one another through welding. This is disadvantageous because the multiplicity of structural parts adversely affects the weight, and the welding operation requires additional measures to effectively eliminate distortions as a result of the welding.
It is thus an object of the present invention to provide an improved shift rocker, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved shift rocker which is optimized as far as weight is concerned and cost-efficient while yet able to satisfy demands as far as strength requirements are concerned.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a shift rocker which is activated through operation of a shift finger, fixedly mounted on a shift shaft, for axially displacing a shift sleeve that is positively connected to a gear wheel clutch or synchronizing unit, with the shift rocker having parallel sidewalls and including a shift slot for positive engagement of the shift finger, and a latch contour for interaction with a stationary shift latching means, whereby the shift rocker is of single-piece configuration and made through a non-cutting process from a blank which is pre-punched from a steel sheet, before being shaped into a finished product by one or more bending operations.
A shift rocker in accordance with the present invention possesses significant weight advantages as a consequence of its single-piece design. Problems experienced with welding operations, such as distortions, are no longer of any concern and thus no additional measures are required, and the overall production costs for a shift rocker of the invention are noticeably less when compared to conventional multi-part shift rockers.
According to another feature of the present invention, the sidewalls are formed from the punched sheet metal strip without punch-out holes from a solid blank, thereby assuring a maximum strength of the shift rocker. By omitting punch-out holes, a further working step is eliminated, further reducing the production costs of the shift rocker.
According to another feature of the present invention, the shift rocker has a cross member, which interconnects the sidewalls, and is provided on both sides with outwardly directed lugs which are formed in one piece with the cross member. After punching the blank, the lugs are bent in a direction away from the sidewalls at a right angle into a parallel relationship to form the shift slot for engagement of a shift finger. Suitably, the shift slot may be disposed substantially in a midsection of the shift rocker to realize a symmetric force introduction in the midsection of the shift rocker, thereby positively affecting the shifting operation and the shifting comfort.
The single-piece configuration of the shift rocker according to the present invention also allows the formation of a latch contour by which the shift rocker can be secured in place in conjunction with a separate, stationary shift latching means. Accordingly, one of the sidewalls has an end portion which is flanged outwardly, preferably at a right angle, along a bending line, with the latch contour of the shift rocker being disposed in the end portion of the one sidewall. Suitably, the latch contour may be impressed during a further bending operation in the respective portion of a sidewall, without requiring further refinishing steps. The one sidewall may have a punch-out hole in an area of the bending line for facilitating formation of the end portion.